Impact of Dietary Lactobacillus Plantarum Postbiotics on Gut Health and Immunity of Layers Under Heat Stress Conditions

Abstract

The effect of feeding lactobacillus plantarum RS5 probiotic and its products on gut health and immune status in laying hens under heat stress were assessed in this study. A total of 192 twenty-week-old pullets of an Isa White strain were randomly assigned in cages in identical environmentally controlled chambers. During the starter period from 1 to 21 days, all the birds were fed the same basal diet. On day 22, the birds were weighed and randomly divided into six treatment groups of 32 birds each. Half of the birds were reared under regular temperature conditions, while the other half was subjected to cyclic daily heat stress gradually reaching about 30°C. Layers were offered one of three different diets: 1) Control, or 2) Control + Lactobacillus plantarum RS5 probiotic, or 3) Control + Lactobacillus plantarum RS5 postbiotic products. The liquid probiotics (RS5 in De Man Rogosa and Sharpe (MRS) broth) and postbiotics (cell free supernatant in MRS broth) were mixed with 100 kg of the feed at a concentration of 200 ml and 300 ml of solution respectively and the feeding trial lasted for 5 months. The study showed that heat stress had a negative impact on the blood profile, mainly on the concentration of red blood cells RBC (2.8 × 106 µl), hemoglobin HGB (11.34 g/dl), hematocrit HCT (27.32 %), mean corpuscular volume MCV (96.26 fl), platelets PLT (35.82 × 103/ml), mean platelet volume MPV (5.53 fl), and plateletcrit count PCT (0.02 ng/ml), where their means showed a significant (p<0.05) decrease compared to control groups at two and five months of the trial. The microscopic and macroscopic intestinal lesions highlighted the influence of probiotic/ postbiotic supplementation in the numerical improvement of the lesions that were caused by heat stress namely, mucosal cells degeneration, deciliation and the number of villi. Dietary probiotics numerically increased the humoral immunity response to Newcastle Disease vaccine at 2- and 4-weeks post vaccination, in comparison to the control group. In addition, the level of antibodies against the Fusion protein was not significantly different among various treatments. In conclusion, both probiotics and postbiotics could be used as a potential alternative antibiotic health promoter and might alleviate the impact of heat stress in the poultry industry. New heat stress models can be evaluated while assessing various dietary probiotics and/or postbiotics in layers.